Are we ready for new form of terror?

He says U.S. actions have prevented it from mounting large scale dramatic attacks

Hayden says smaller-scale attacks are difficult to defend against

He says question for a free society is how much security it will accept

Editor's note: Gen. Michael V. Hayden was appointed by President George W. Bush as CIA director in 2006 and served until February 2009. He also was director of the National Security Agency and held senior staff positions at the Pentagon and is now a principal with The Chertoff Group, a security consulting firm.

(CNN) -- Members of the Obama administration, such as Michael Leiter, director of the National Counter Terrorism Center, have been using every public opportunity in recent weeks to tell the nation that the threat from al Qaeda has changed.

Not that Leiter needs me to validate his conclusions, but he's right. Now huddled in the tribal regions of Pakistan, the organization that attacked us on 9/11, al Qaeda main, has been roughly handled.

Because of the actions of two successive administrations, much of this enemy's senior leadership had been captured or killed -- recently, more the latter than the former. What remains of that leadership spends a lot of its waking moments worried about ensuring its own survival rather than threatening ours.

Steps taken to enhance American intelligence and to increase cooperation within the American intelligence community and between American and foreign intelligence services are also paying dividends.

The classic al Qaeda attack, inflicting mass casualties by hitting iconic targets, is now very difficult for them to mount. Such attacks take time to prepare and have multiple threads: logistics, recruiting, training, operations, finance. We have become much better at detecting these threads and rolling up these plots. The 2006 airliner plot in the United Kingdom, for example, might well have succeeded if it had been mounted against our intelligence services as they existed in 2001, but not in 2006, or now.

But we are far short of arranging a victory celebration. Al Qaeda's capacity to mount its traditional brand of spectacular attacks has been reduced, not eliminated. And this is a learning, adaptive and determined enemy.

The new flavor of al Qaeda's threat is lower threshold, less centrally managed and more local. The 2009 Christmas Day attack on an airliner as it approached Detroit, Michigan, was the first attack on our homeland that did not have a thread that took it back to al Qaeda main in Pakistan. It was mounted by an al Qaeda franchise in Yemen and conducted with little training or vetting of the attacker since the enemy knew they risked the operation's compromise with any deeper contact with him.

Other recent threats -- Times Square and the New York City subway -- have been similarly lower threshold and these were engineered by long-term residents of the United States.

This shift is what we in the intelligence community feared as we, like other Americans, watched cable news coverage of the carnage in Mumbai nearly two years ago. Beyond lamenting the immediate tragedy, we anticipated that al Qaeda would go to school on the attacks and see that a small number of terrorists with simple weapons and cell phones could achieve the kind of macro political and economic impact that they had always pursued.

And go to school they have. Future threats will likely be less complex, less well-organized, less likely to succeed, less lethal when they do -- but unfortunately, more frequent.

And American intelligence must adapt, once again. But adapting carries with it serious political and policy questions that should be addressed and which spokesmen such as NCTC's Leiter are implicitly teeing up in their very public characterization of the threat.

Our current successes against al Qaeda have been hard won, not just operationally but also in a legal and a policy sense. Although there are some troubling exceptions, we have worked to an adequate national consensus on many aspects of this war -- that it is indeed a war, that we can kill or detain our enemies, that we can tolerate more government intrusion into our convenience, commerce or privacy.

Al Qaeda's capacity to mount its traditional brand of spectacular attacks has been reduced, not eliminated.--Michael V. Hayden

So we will continue to take the fight to the enemy, keeping him off balance and less capable of his preferred "spectaculars." But it is unlikely that the existing consensus, which has served us well enough for yesterday's threat, is adequate for today's threat, which will certainly be harder to detect and be more domestic in its origins. And if the current consensus is not adequate, what should we do?

A year ago at an international conference in Geneva, Switzerland, I discussed this question with Sir David Omand, former chief of intelligence in the British Cabinet Office.

He outlined the problem starkly: Intelligence services in free societies operate within the bounds that their societies set. But as part of that "social contract," those societies implicitly admit that their choices -- the limits they choose to place on their intelligence services -- inescapably affect the margins of their safety.

Speaking practically and metaphorically, how much more are we willing to take off in the security line at Dulles Airport? More generally, what will it take to be able to confidently keep lone suicide bombers off commercial airliners or errant SUVs driven by self-radicalized American citizens out of Times Square?

What portion of what we might do will we be willing to actually do? And for the remainder, are we willing as a nation to recognize and accept the risk of doing less than we otherwise might?

This dialogue will take courageous political leadership, and that's really the issue that Leiter and others want addressed. What they fear is that we will again pretend that there are no such hard choices. Remember the campaign mantra that it is a false choice between our values and our security. Or remember the frenetic claims after Detroit that we will take steps to ensure that this never happens again?

Collectively intelligence professionals fear a continuation of an attitude that feels free to blame the intelligence community for doing too much when Americans feel safe and for doing too little when they don't.

And finally -- absent the mature dialogue that Omand calls for -- they fear another spasmodic political response after the next perceived failure, a spasm that will do more harm than good to the people and the institutions that are actually quite successful in defending us.

The opinions expressed in this commentary are solely those of Michael V. Hayden.